1. Field of the Invention
The present invention relates to an information processing device and method, program, and recording/reproducing device, and specifically, relates to an information processing device and method, program, and recording/reproducing device which enable an initial value to be compensated in a more suitable manner with a control system for controlling the operation of an object of control to direct the angle or position thereof toward a target value.
2. Description of the Related Art
Heretofore, with an optical disc recording/reproducing device, servo control has been performed to condense a laser beam to a fixed position. Specifically, focus servo control for correcting condensed position shift in a disc-vertical direction, and tracking servo control for correcting condensed position shift in a disc-radial direction are performed. A servo controller is realized generally by the following filter for emphasizing low-frequency components, and performing phase shift compensation at a high frequency. Specifically, a filter is employed, which emphasizes the low-frequency components of an error signal to suppress low-frequency position shift, performs compensation of phase shift at a high frequency, thereby operating a control system in a stable manner.
This error signal is generated under reflected light from an optical disc, but a detection region whereby a normal error signal can be detected is limited. Therefore, for example, with the focus servo control, a lens mounted on an actuator is driven to a detection region, and confirmation is made whether or not the lens is in the detection region, following which a servo control operation is started. Also, with the tracking servo control, the detection region is relatively swung as to the lens in a stationary state due to disc eccentricity, and accordingly, a servo control operation is started while considering a point in time wherein relative speed is slow.
As described above, at a point in time where a servo control operation is started, the relative position and relative speed of the actuator as to a target position are frequently not zero. At this time, the relative position or relative speed is sufficiently small, and the actuator position converges at the target position through transient response. However, if the relative position or relative speed is great (not sufficiently small), the actuator position protrudes from the detection region due to saturation of actuator thrust during transient response, or the like, and consequently, the actuator position does not converge at the target position in some cases.
In order to suppress occurrence of such a situation, techniques have been generally employed, such as a servo control operation being started at a position where the relative position is as small as possible, speed servo control being performed before a servo control operation is started to reduce the relative speed, or the like.
Also, a technique has been proposed wherein a transient response correction value is charged in a capacitor within an integrator of a servo controller before start of the servo control, and with this as an initial value of the integrator, the servo control is started, thereby reducing transient response (e.g., see Japanese Unexamined Patent Application Publication No. 1-138666). Further, a technique has also been proposed wherein compensation quantity corresponding to the properties of an object of control is obtained, or the initial settings of a servo controller are performed by obtaining a coefficient to compute an initial value, thereby performing a positioning operation in a stable manner (e.g., see U.S. Pat. No. 2,685,622). In this way, techniques have been proposed wherein stable transient response is obtained by setting the initial value of the servo controller to a suitable value to perform initial value compensation.